A Continuum Damage–Cohesive Zone Modeling Framework for Filament and Interlayer Fracture in 3D-Printed Concrete (2026-04)¶

This study investigates the fracture behavior of hardened 3D Printed Concrete (3DPC) with particular emphasis on the roles of filament cracking and interlayer debonding. Due to the layer-by-layer deposition process, 3DPC exhibits anisotropic mechanical behavior, with fracture response strongly dependent on filament orientation, printing path, and interlayer bonding quality. Understanding these fracture mechanisms is essential for evaluating the structural performance and reliability of printed concrete elements. A numerical modeling framework is developed to separately represent damage in the printed filaments and fracture at the interlayer interfaces. Filament behavior is modeled using a continuum damage mechanics approach to capture progressive stiffness degradation and distributed cracking in the bulk material. Interlayer regions are explicitly modeled using cohesive-zone models, allowing simulation of crack initiation and propagation along layer interfaces. The framework clearly distinguishes between filament-controlled and interface-controlled failure modes.The model is applied to simulate flexural fracture of printed concrete beams under different printing configurations, examining the influence of printing path and time interval between layers. The model predictions, in agreement with experimental observations, demonstrate that the printing path significantly influences flexural performance, with crack propagation across filaments yielding higher load capacity and fracture resistance than interlayer-dominated failure. Additionally, increasing the time interval between layers reduces fracture energy and weakens interlayer bonding, leading to lower load-carrying capacity. These findings highlight the critical role of interface quality in governing fracture behavior and emphasize the necessity of accounting for both filament damage and interlayer fracture in the structural analysis of 3DPC.